Relation of protease production to nematode-degrading ability of two Arthrobotrys spp.

A comparison of the nematode-destroying capability of two nematophagous Arthrobotrys spp. (coded ART-1 and ART-2), isolated from soil samples, showed that ART-1 (LD50 = 290 conidia/ml) was more efficient than ART-2 (LD50 = 725 conidia/ml). The two isolates produce extracellular proteases in liquid culture. The proteases from both isolates had a temperature optimum of 50 degrees C. The optimum pH for protease activity was in the range of 7.5-8 for ART-1 and 7.5-9 for ART-2. ART-1 produced more protease activity (13.3 +/- 0.72 U/ml) than ART-2 (10.9 +/- 0.375 U/ml). The proteases from ART-1 were more efficient in degrading nematodes than those of ART-2 by virtue of being produced in a larger quantity. We suggest that the difference in the nematode-destroying capability between the two strains is solely the result of the difference in the amount of extracellular proteases they produce.